These studies involve humans (or human tissues) and can be divided into two areas. First, systematic assessment of adrenergic status--sympathoadrenal catecholamine release, plasma catecholamine kinetics, beta-adrenergic receptors and plasma catecholamine concentration dose-response relationships with metabolic (and hemodynamic) actions--in patients with diseases in which altered adrenergic status can be hypothesized to be present. An example is diabetes mellitus. Second, study of the mechanisms of normal nonhypoglycemic glucose counterregulation-the prevention of hypoglycemia--in the postprandial and postabsorptive state to define those factors that are physiologically relevant (be they hormonal, neural or autoregulatory). These include, but are clearly not limited to, study of the role of the sympathoadrenal system.